The present invention is directed to a device for reducing the frictional drag of moving bodies, particularly vehicles, such as airborne, waterborne and space vehicles. The invention is thus concerned with a phenomenon which is inherent in flow mechanics.
The no-slip condition of flow in fluid mechanics indicates that an interface of a flowing medium with the wall of a moving body, flow velocity and wall velocity are identical. As a consequence of the no-slip condition and the viscosity, each body moved through a stationary medium tends to drag along with it a portion of the medium next to it and behind it. As a result, the speed or velocity of the moving body will be slowed down. The frictional drag of airborne and waterborne vehicles is thus a direct consequence of the no-slip condition in flow mechanics.
More than half of the fuel used in aviation is required for overcoming frictional drag. If it were possible to produce a certain slip between the flowing air and the aircraft surface, the frictional drag could be reduced and the economics of aircraft operation would be considerably improved. Relative drag reduction may be expressed in the following formula: ##EQU1##
The adhesion of liquid or gas particles in proximity to the wall of a moving body can be explained by the affinity between the molecules of the flowing medium and the atoms of the wall.